Central buffer couplings of the Scharfenberg design have been known, in which an approximately semicircular groove, into which a heating element is placed, is provided in the buffer surface of the coupling head in the area of the centering cone and of the funnel. The heating element shall keep the front faces and the coupling mechanism free from ice and snow in the winter and ensure the function of the coupling. The groove is closed to the outside by a hard solder, which forms part of the buffer surface. Only low-melting hard solders, e.g., expensive silver filler, can be used as hard solders, because there is a risk of damage to the heating element at higher processing temperatures.
The use of soft solders with lower melting point proved to be unsuitable, because the melting point of the soft solder was frequently reached at the required heat output of the heating element.
It has also been known that the groove can be closed to the outside by welded-in cover plates. The possible warping of the cover plates as well as of the front plate due to the increased supply of heat during welding must be borne in mind and taken into account. Uneconomical preparatory procedures of the groove with ground contact for the cover plate and uneconomical finishing operations, especially the leveling of the weld seam, are necessary. Besides the possible damage to the heating element due to the welding process, there always is a risk of penetration of moisture into the cavity and consequently of damage to the heating element.